package com.phone580.app.untilty;

import java.io.ByteArrayOutputStream;

public class MyBase64 {
	
	
	private static final char[] encodeTabel = {
											'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',  
									        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',  
									        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',  
									        'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',  
									        'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',  
									        'o', 'p', 'q', 'r', 's', 't', 'u', 'v',  
									        'w', 'x', 'y', 'z', '0', '1', '2', '3',  
									        '4', '5', '6', '7', '8', '9', '+', '/'};
	
	
	private static final byte[] decodeTabel = {
											-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  
										    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  
										    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,  
										    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,  
										    -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,  
										    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,  
										    -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,  
										    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1};
	
	public static String encode(byte[] bs, int offset, int length)
	{
		StringBuffer sb = new StringBuffer();
		int a,b,c;
		while (offset < length)
		{
			a = bs[offset++] & 0xff;
			if (offset == length)
			{
				sb.append(encodeTabel[a >>> 2]);
				sb.append(encodeTabel[(a & 0x03) << 4]);
				sb.append("==");
				break;
			}
			
			b = bs[offset++] & 0xff;
			if (offset == length)
			{
				sb.append(encodeTabel[a >>> 2]);
				sb.append(encodeTabel[((a & 0x03) << 4) | ((b & 0xf0) >>> 4)]);
				sb.append(encodeTabel[(b & 0x0f) << 2]);
				sb.append("=");
				break;
			}
			
			c = bs[offset++] & 0xff;
			sb.append(encodeTabel[a >>> 2]);
			sb.append(encodeTabel[((a & 0x03) << 4) | ((b & 0xf0) >>> 4)]);
			sb.append(encodeTabel[((b & 0x0f) << 2) | ((c & 0xc0) >>> 6)]);
			sb.append(encodeTabel[c & 0x3f]);
		}
		
		return sb.toString();
	}

	
	public static byte[] decode(String s)
	{
		if (s == null) {
			return null;
		}
		byte[] bs = s.getBytes();
		int length = bs.length;
		ByteArrayOutputStream baos = new ByteArrayOutputStream(length);
		int offset = 0;
		int a,b,c,d;
		while (offset < length)
		{
			do {
				a = decodeTabel[bs[offset++]];
			} while (offset < length && a == -1);
			
			if (a == -1)
			{
				break;
			}
			
			do {
				b = decodeTabel[bs[offset++]];
			} while (offset < length && b == -1);
			
			if (b == -1)
			{
				break;
			}
			
			baos.write((a << 2) | ((b & 0x30) >>> 4));
			do {
				c = bs[offset++];
				if (c == 61)
				{
					return baos.toByteArray();
				}
				
				c = decodeTabel[c];
			} while (offset < length && c == -1);
			
			if (b == -1)
			{
				break;
			}
			
			baos.write(((b & 0x0f) << 4) | ((c & 0x3c) >>> 2));
			do {
				d = bs[offset++];
				if (d == 61)
				{
					return baos.toByteArray();
				}
				
				d = decodeTabel[d];
			} while (offset < length && d == -1);
			
			if (d == -1)
			{
				break;
			}
			
			baos.write(((c & 0x03) << 6) | d);
		}
		
		return baos.toByteArray();
	}
	

}